This invention relates to improvements in steering column assemblies.
It is known to provide a steering column for a vehicle in which a steering column shaft is supported within a telescopic shroud that is fixed to the body of the vehicle, usually to a beam located behind the dashboard. The steering column shaft protrudes from one end of the shroud and is connected to a steering wheel that the driver can turn to rotate the shaft and hence steer the vehicle. The steering column shaft is typically connects to the road wheels through gearbox and an electric motor may be provided which provides useful torque that assists the driver in turning the steering wheel. The telescopic shroud permits adjustment of the position of the wheel relative to the driver. The position may be adjusted for reach by allowing, in an unclamped condition, for one part of the shroud to telescope over or into another part of the shroud. In many cases the steering column assembly will also allow adjustment for rake in the unclamped condition by allowing the whole shroud to be moved relative to the body of the vehicle. This is typically achieved by the shroud pivoting about a pivot axis located some distance from the steering wheel.
There are two basic types of telescopic or so-called “Tube-in-Tube” steering column assemblies. This invention relates to the type known as a “Cantilever” or “Inverted” Tube-in-Tube type in which the shroud comprises a hollow outer part, typically a tube, that slides over a hollow inner part, also typically a tube, within which the steering column shaft is supported. The inner tube is located nearest the steering wheel and is the one that moves for reach, sliding into the outer Tube that is secured to the vehicle body further away from the steering wheel. The outer tube typically cannot move axially but can pivot around a pivot axis. The inner tube can move during adjustment when the assembly is an unclamped condition. The inner tube should also be able to move axially during a crash, even when the assembly is in a clamped condition, and this movement is typically resisted by an energy absorbing mechanism to control the collapse of the steering column assembly.